This invention relates generally to filters and dust collectors and, more particularly, to apparatus of this general type which includes some arrangement for automatically cleaning the filter media continuously or at periodic intervals.
There are many types of filters and dust collectors which include some form of filter media through which transport air or other fluid having dust or other foreign matter is entrained therein passed to deposit the foreign matter on the exposed surface of the filter media, and in industrial and similar heavy-duty applications where the filtered foreign matter collects on the surface of the filter media at a relatively rapid rate. It is desirable to provide the apparatus with some form of automatic cleaning of the filter media so that it can be run on a continuous basis.
For example, the typical industrial bag-type filter includes some form of reverse air flow, or "backwashing," of cleaning air opposite to the normal flow of the transport air which lifts the foreign matter collected on the exposed surface of the bag off of the bag so that it can gradually migrate downwardly to the bottom of the filter apparatus where it can be collected and removed. Similarly, in typical pleated paper filters, a high pressure pulse of cleaning air is passed back through pleated paper filter cartridges to move the foreign matter away from the surface of the filter media. In cleaning arrangements of this type, the efficiency of the cleaning is reduced by the fact that the foreign matter, when it is temporarily moved away from the surface of the filter, is not immediately transported away from the filter, but is instead allowed to sometimes be re-entrained in the transport air and brought back to tire surface of the filter, albeit at a different (e.g., lower) location on the filter.
In other types of filters, belts or substrates of filter media are used, and because of the nature of such filter media it is possible to use a suction nozzle positioned adjacent the surface of the substrate for removing the collected foreign or particulate matter therefrom and then using the suction to transport the foreign or particulate matter away from the filter for collection and removal. In some filters of this type, the flat filter is stationary and the cleaning nozzle is moved across the surface of the filter media as disclosed, for example in Williams U.S. Pat. No. 4,725,292, and in other designs the filter media is moved past a stationary suction nozzle. While the efficiency of the cleaning apparatus in these filters is very high since the foreign matter is positively removed from the filter media and carried away, the filtering efficiency of the filter apparatus itself is relatively small because the filter media is in a flat or planar form which, for a given size of filter apparatus, offers a relatively low air-to-cloth ratio as compared, for example, with the above-described pleated paper filters.
In accordance with the present invention, a unique filtering apparatus and method are provided which combines the high cleaning efficiency of belt-type filters with the high filtering efficiency of filters having a pleated filter media.